This invention relates to a dock leveler used to bridge the gap between a loading dock and the bed of a truck or carrier parked adjacent the loading dock, and more particularly to improvements in dock levelers incorporating an airbag or other inflatable member for raising the ramp of the dock leveler.
A dock leveler typically includes a frame or supporting structure mounted in a pit or depression in the loading dock. The rear end of a ramp or deck plate is pivotably mounted to the supporting structure so that the ramp is movable between an inclined position in which the ramp is supported by the truck bed, a horizontal inoperative position, and a raised position in which the forward end of the ramp is raised above the truck bed.
An extension lip is pivotably mounted to the forward end of the ramp, and is movable between a downwardly hanging pendant position and an extended position in which the lip forms an extension to the ramp.
After a truck has parked in front of the loading dock in preparation for a loading or unloading operation, the ramp of the dock leveler is raised to its upwardly inclined position. As the ramp is lowered, the lip is pivoted outwardly to its extended position. As the ramp is subsequently lowered, the lip engages the bed of the truck to support the ramp, such that the ramp and the lip in combination bridge the gap between the loading dock and the truck bed. After the loading or unloading operation is completed, the ramp is raised and the lip falls by gravity to its pendant position. The ramp is then lowered to its horizontal position, and the truck can then pull away from the loading dock.
In the past, the ramp has been pivoted to its upward position in response to operation of a mechanical or hydraulic mechanism. However, recent developments in the dock leveler art disclose an inflatable member or bag utilized to pivot the ramp to its upwardly inclined position, such as is illustrated in copending U.S. patent applications Ser. No. 08/131,983 filed Oct. 4, 1993 and Ser. No. 08/131,988 filed Oct. 4, 1993. These applications disclose a bag inflated with low pressure air by an inflating device such as a fan or blower, and are hereby incorporated by reference.
The present invention is directed to improvements in a dock leveler, and more particularly to improvements providing advantageous construction, operation and servicing of a dock leveler incorporating an inflatable member for raising the ramp between its raised and lowered positions.
In accordance with one aspect of the invention, the inflatable member is mounted to a support disposed below the ramp and the inflating device, such as a fan or blower, is likewise mounted to the support. The lower portion of the inflatable member is supported by an upwardly facing surface defined by the support, and the inflating device is mounted to a downwardly facing surface defined by the support. An opening is formed in the support, and the inflating device communicates with the interior of the inflatable member through the opening. The support defines a forward end and a rearward end, and the rearward end of the support is mounted below the ramp so as to be raised above the pit floor. The forward end of the support is lowered relative to the rearward end, and is preferably engaged with the pit floor. The fan is mounted adjacent the raised rearward end of the support, so as to elevate the fan above the pit floor. In a preferred form, the rearward end of the support is removably mounted below the ramp via a mounting arrangement in which engagement of the support is released by upward movement of the rearward end of the support. One or more wheels are located adjacent the forward end of the support and are engageable with the pit floor. The support, inflatable member and inflating device are removable as a unit from the dock leveler by disengaging the rearward end of the support from the dock leveler and drawing the support, inflatable member and fan forwardly as a removable subassembly. This feature provides relatively quick and easy removal of the support, inflatable member and inflating device, to facilitate servicing and/or replacement of such components.
In accordance with another aspect of the invention, a selectively actuable lifting device, preferably but not necessarily in the form of an inflatable member, is employed for selectively moving the ramp to its raised position from its lowered position. The lifting device is supported by a support having forward and rearward ends. The lifting device support is raised in order to facilitate access to the rearward portion of the pit by pivotably mounting the rearward end of the lifting device support above the pit floor, engaging a lifting tool in an engaging position with the lifting device support adjacent its forward end, and moving the lifting tool to an operative lifting position in which a portion of the lifting tool is disposed between the forward end of the lifting device support and the pit floor. In this manner, the forward end of the lifting device support is raised above the pit floor, and the lifting device support is pivoted about the pivotable connection of the lifting device support rearward end. The lifting tool includes a first section engageable with the forward end of the lifting device support, and a second section interconnected with the first section and engageable with the pit floor when the lifting tool is in its operative lifting position. One or more wheels are interposed between the first and second sections of the lifting tool. In one form, the lifting device support includes one or more wheels mounted to a transverse axle, and the step of engaging the lifting tool with the lifting device support is carried out by engaging the lifting tool with the axle. The lifting tool first section is arranged relative to the lifting tool second section such that, when the lifting tool is in its operative lifting position, the point of engagement of the lifting tool with the lifting device support is located forwardly of the wheel, between the wheel and the point of engagement of the lifting tool second section with the pit floor. This provides a stable structure for maintaining the lifting device support in its raised position until removal of the lifting tool.
In accordance with another aspect of the invention, the rear end of the lifting device support is removably and pivotably mounted below the ramp via a mounting arrangement in which engagement of the lifting device support is released upon upward movement of the rearward end of the lifting device support. One or more wheels are mounted toward the forward end of the lifting device support and the forward end of the lifting device support is raised, either by the structure and method set forth in the preceding paragraph or in any other satisfactory manner. After raising of the lifting device support, one or more second, auxiliary wheels are mounted to or otherwise positioned on the lifting device support. The auxiliary wheels are mounted at an elevation below the first-mentioned wheels. The lifting device support is then lowered to engage each auxiliary wheel with a rolling surface, which could be the pit floor but which preferably is an upwardly facing surface defined by longitudinal front-to-rear extending side frame members located above the pit floor, such that the first-mentioned wheels are located thereabove. A downward force is then exerted toward the forward end of the lifting device support while the auxiliary wheels are engaged with the rolling surface, to cause an upward movement of the rearward end of the lifting device support to release engagement of the lifting device support. The lifting device support is then removed by exerting a forward force on the lifting device support while maintaining engagement of the auxiliary wheels with the rolling surface. As before, the lifting device is preferably in the form of an inflatable member mounted to the support, and an inflating device is also mounted to the support such that removal of the support results in simultaneous removal of the inflatable member and the inflating device. The step of removably and pivotably mounting the lifting device support below the ramp is carried out by engaging a pin provided toward the rearward end of the support within an upwardly facing recess formed in a depending member extending downwardly from the ramp. The step of raising the forward end of the lifting device support is preferably carried out as set forth in the preceding paragraph, by engaging a lifting tool with the forward end of the lifting device support and moving the lifting tool to an operative lifting position to raise the forward end of the support. The step of mounting one or more auxiliary wheels to the support is preferably carried out by providing one or more auxiliary wheel assemblies, each of which includes a mounting plate having an upper end and a lower end to which an auxiliary wheel is mounted, and removably mounting the upper end of each mounting plate to the lifting device support.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.